文章通过建立精细的三维有限元模型,运用数值模拟方法对运行工况下高压隧洞区域的渗流场和渗漏量进行分析,对岩体水力劈裂风险性和渗透稳定性进行了评估,并对参数进行了敏感性分析.在高压隧洞区防渗排水系统的作用下,隧洞内水外渗得到有效控制,发生渗透破坏的可能性较小.

Packer test is a tool that has been long developed and widely used for characterizing the permeability of formation. The flow in the tested formation tends to transition from laminar to non-Darcian regime with increasing flow velocity and hydraulic gradient. But as the non-Darcian effect becomes important, how the borehole inclination and groundwater level influence the interpretation of packer test data remains unclear. In this study, a Forchheimer's law-based analytical model incorporating the effects of groundwater level and borehole inclination was presented by image method and velocity integration, which can be immediately reduced to Zangar's (1953) equation for vertical borehole under laminar flow condition and approximately reduced to Chen's (2015b) model when the test interval is at a moderate depth below the groundwater level. The proposed model was validated by numerical simulations. Parametric and error analyses indicate that the hydraulic conductivity will be overestimated while the non-Darcy coefficient will be underestimated if the effects of groundwater level and borehole inclination are neglected. The proposed model was applied to data interpretation of packer tests performed in fractured sedimentary rocks in Hainan Province, China. The results show that significant non-Darcian flow occurred in the tests. The borehole inclination has little influence on the estimation of hydraulic parameters, but demonstrates the anisotropy and heterogeneity of the rocks.

岩体的渗透系数是渗流场分析与工程渗控设计的重要参数,钻孔压水试验是获取该参数的主要方式之一.针对地下水面下有界渗流区域中倾斜钻孔压水试验数据解析问题,基于Darcy定律和镜像法建立了岩体渗透系数解析模型,并对该模型进行了数值验证.该解析模型形式简洁,物理意义明确,且在钻孔试段离地下水位较远时可退化为现行钻孔压水试验规程推荐的Hvorslev公式,是现行压水试验数据解析方式的理论拓展,可作为钻孔压水试验规程修订的重要依据.

夹层结构或互层结构是常见的坡体结构形式,软弱夹层或岩层通常具有较弱的透水性,对边坡地下水分布及渗透特性具有重要影响.基于水体质量守恒方程及V-G模型,采用PVI方法对含夹层边坡进行非饱和渗流模拟.通过实验对比,验证了该算法的可靠性.现场尺度的模拟结果表明,含低渗透性夹层的边坡易在夹层处表现出地下水分层的现象,且夹层的渗流特性和发育程度直接影响该区域地下水的分布情况:随着夹层非饱和参数α的增大(或n的减小),夹层与邻近岩土体渗透系数比的减小,夹层厚度与高度的增加,地下水分层现象更加显著.研究揭示了含夹层边坡地下水特殊分布模式,也对类似结构岩土体的非饱和水力参数确定有一定的参考价值.

Aquifers with quasi-linear flow pattern are frequently envisaged in fractured zones, in oil, gas or enhanced geothermal reservoirs, or in civil engineering where cut-off walls are constructed. The water flow towards a well in this linear aquifer system has been long investigated under Darcian flow condition, but remains an open issue for non-Darcian flow. In this study, a general linearization approximation strategy is suggested for the Forchheimer equation, and an analytical solution is proposed by using Laplace transform for non-Darcian flow towards a well in aquifers laterally bounded by no-flow barriers. Numerical simulations using the finite volume method prove that the linearization approximation performs best when it takes the mean of two commonly-used strategies, and the analytical model is sufficiently accurate at late times for observation wells located moderately far from the source. The proposed model was applied to data interpretation of the pumping tests at the Changheba dam foundation bounded by two cut-off walls in Southwest China, where the drawdown curves can be divided into 1D flow, transitional flow and 2D flow stages as a result of lateral flow through weathered bedrocks at late times. The proposed model provides a valuable tool for characterizing the hydraulic properties of aquifers and reservoirs with a linear flow pattern and for assessing the possible leakage through the lateral barriers by type curve matching.

高拱坝地处深切河谷,岸坡陡峻,岩体卸荷强烈,地质条件复杂.水库蓄水后,坝基岩体将承受较大的渗透水压和渗透坡降,渗流控制是工程建设的关键问题之一.结合我国西南地区某高拱坝工程,建立反映坝址区地形地貌、地质构造、枢纽布置和防渗排水系统的三维整体有限元模型,采用排水子结构、变分不等式以及自适应罚函数相结合的渗流分析方法,研究了厂坝区三维渗流场的分布特征,并评价了防渗排水系统的有效性.研究表明,厂坝区防渗排水系统排水降压效果显著,不仅厂坝区的地下水位和渗漏量得到有效的控制,且主要断裂构造的渗透稳定性满足工程安全要求.